Static pose fixture

ABSTRACT

The present invention relates to a static pose fixture ( 10 ) used for measuring a subject ( 42 ) that is the object of a motion capture system. The static pose fixture ( 10 ) provides a means for holding the subject ( 52 ) in a static position by using various struts in order to automate the sizing of a computer generated model or to position and orient markers with respect to the model.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 10/708,431 filed on Mar. 3, 2004, which is adivisional application of U.S. patent application Ser. No. 10/064,739,filed on Aug. 12, 2002, now U.S. Pat. No. 6,702,691.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a static pose fixture that is utilizedin motion capture systems. More specifically, the present inventionrelates to a static pose fixture utilized to measure geometry and bodyplate marker locations of a subject for preparation of a motion capturemodel during a golf swing.

2. Description of the Related Art

Motion Capture is used to measure the position and or orientation of anyobject, usually at multiple points in time. There are four maincategories of motion capture devices, mechanical, magnetic, passiveoptical, and active optical. An example of a mechanical device is theCyberglove®. A mechanical device measures the orientation of rigid linksmounted to a subject. A magnetic device such as the AscensionMotionStar® or Polhemus StarTrak® measures the position and orientationof wire coils attached to the subject. Since golf clubs are typicallyconstructed of metal or metal parts, magnetic systems, which may looseaccuracy when metal objects are near by, may experience some distortionduring a golf swing motion measurement. Passive optical systems usemultiple cameras to triangulate the position of reflective markersplaced on the subject. Exemplary examples of a passive optical systemare those made by Vicon and Motion Analysis. Active optical systems usetriangulation to track the position of infrared light emitting diodes.Exemplary examples of active optical systems include systems such asNorthern Digital's Optotrak and Charnwood Dynamics CODA. Active opticalsystems have the ability to distinguish markers from one another, whichgreatly decreases the time it takes to process data and which makes thema preferred device for use with the static pose fixture as describedherein, however, any of the devices as previously discussed may be used.

An active optical motion device is able to determine the position andorientation of a rigid object as long as 3 non co-linear markers on thatobject are in view of the sensors. An occluded marker is a marker thatis not in view of any of the sensors. One marker on a rigid body plateis selected to be the origin of a coordinate system. The 3D position ofeach marker on the plate is measured, and the position and orientationof the plate is then reported with respect to the global origin. Togenerate the best possible motion capture data, it is important to havemore than 3 non co-linear markers on each rigid body to increase thechances that at least three markers on the body are not occluded, sincethe object itself can come between a marker and a sensor.

To drive a computer generated human model with motion capture, datamarkers of any type (retro-reflective, active IRED, magnetic, etc.), aremounted on the subject in areas where the motion must be acquired. Thesubject is then asked to stand straight with arms in a horizontalposition, thus forming a cross with the body. A frame of data isacquired in the form of a point cloud. Within the software, the operatorthen moves the human model into the point cloud so that each marker isnear the same location within the model as on the subject. If thesubject has not assumed the exact same posture as the default posture ofthe model, the operator rotates the limbs to mimic the subject'sposture. If the subject is a different size compared to the model, theoperator lengthens or shortens each limb so that it looks correct. Oncethe model is sized and oriented properly within the point cloud, theconfiguration is saved and any further motion data acquired from thesubject can be used to drive the motion of the model. Some humanmodeling software allows the user to measure body segments and inputvalues, which can increase accuracy but is relatively time consuming.

Several methods of capturing motion data have been proposed includingNesbit et al., U.S. Pat. No. 5,772,522, which discloses the analysis andmeasurement of a representative model during an active motion such as agolf swing.

Further examples include Kramer, U.S. Pat. Nos. 5,592,401 and 6,148,280,which disclose the use of sensor devices placed on a subject during anactive motion, like a golf swing, thereby enabling the capture andanalysis of the motion.

Still more examples include Haas et al., U.S. Pat. No. 4,137,566, whichdiscloses the use of a plurality of reflective sources and a datacollector to record active motions, like golf swings, for analysis.Mann, U.S. Pat. No. 4,891,748, discloses using video images inpreparation of computer generated models.

However, the process of sizing and orienting the model in the pointcloud is time consuming and inaccurate. Because the orientation of eachlimb in space is estimated by the operator, it is subject to variationand inaccuracy. If it is assumed that the subject is standing with armsperfectly horizontal when the arms are actually skewed slightly or bent,the location of markers on the wrists of the subject will be modeledwith a high degree of inaccuracy. As motion capture data is used todrive the model, this inaccuracy will cause the wrist to be driven to alocation that is offset from the measured location. When modeling a golfswing, even slight inaccuracy in the wrists can lead to large inaccuracyin the location of the club head, rendering the model far less useful.Additionally, if any of the markers move with respect to the subjectonce the model generation is complete, the process must be repeated fromthe beginning or further inaccuracy will result.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a fixture for holding a motion capturesubject in a static position in order to automate the measurements ofgeometry and marker locations. In using motion capture for swingmodeling, it is critical to accurately depict the subject that is theobject of the motion capture. By using the static pose fixture, thesubject is constrained to a static position enabling the pre set bodyplates to be measured for accurate joint segment length, body angledepiction and body orientation measurements to be used to accuratelydepict on the model of the motion capture subject.

Furthermore, the present invention enables a technician to make accuraterepeatable measurements and eliminates a vast number of steps previouslyrequired to perform the measurements and removes variables thattypically lead to inaccuracy in designing computer generated models usedin motion capture. By identifying and measuring body plate locations ofthe subject while in the static pose fixture, the static pose fixturealso provides a means to automatically position and orient motion agentscorresponding to the body plate locations on the model for achievingaccurate repeatable subject data.

Moreover, if a body plate moves during the modeling process as oftenhappens, the static pose fixture provides a means to rapidly andautomatically re-position the subject's body plate location formeasuring segment length, body angle or body orientation, whereaswithout the static pose fixture, the entire marker orienting processneeds to be repeated from the beginning.

Having briefly described the present invention, the above and furtherobjects, features and advantages thereof will be recognized by thoseskilled in the pertinent art from the following detailed description ofthe invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a perspective view of the static pose fixture of the presentinvention.

FIG. 2 is a back plan view of the static pose fixture of the presentinvention.

FIG. 3 is a side plan view of the static pose fixture of the presentinvention.

FIG. 4 is a front view of a subject with attached body plates in thestatic pose fixture.

FIG. 5 is a side view of a subject with body plates attached in thestatic pose fixture.

FIG. 6 is a perspective view of an alternative embodiment of the staticpose fixture as described herein.

FIG. 7 is an illustrative example of an exemplary grip as used on thestatic pose fixture.

FIG. 8 is an illustrative example of a body plate with marker formeasuring the position and orientation of the subject's limbs while inthe static pose fixture.

FIG. 9 is an illustrative example of a slider with marker for takingjoint center measurements.

FIG. 10 is an illustrative example of a joint center measurement takenusing a digitizing probe.

FIG. 11 is a graph of the computer modeling process using the staticpose fixture as described.

FIG. 12 is a front view of a computer generated model in the static poseposture with motion agents applied.

FIG. 13 is a side view of a computer generated model in the static poseposture with motion agents applied.

FIG. 14 is a view of a computer generated model in ball address positionas modeled using the static pose fixture.

FIG. 15 is an example of a computer generated model stepping throughswing data generated by the computer program using the measurementsestablished while in the static pose fixture and club selection data.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated in FIG. 1, a static pose fixture for measuring the sizeof a motion capture subject 52 is generally designated 10. The staticpose fixture 10 of the present invention includes a base 12, first andsecond foot alignment struts 16 and 18, first and second vertical struts20 and 22, first and second grips 26 and 28 and first and second sliderstruts 30 and 32.

The base 12 is preferably substantially flat. The base 12 preferably hasa plurality of wheels 14, to provide the fixture 10 with mobility.

As illustrated in FIGS. 1-3, first and second foot alignment struts 16and 18 for placement of a right and left foot of a subject 52 arelocated on the upper exterior portion of the base 12. The first andsecond foot alignment struts 16 and 18 are preferably placed at least 4inches from the rear portion of the base 12. The distance d between thefirst foot alignment strut 16 and the second foot alignment strut 18 ispreferably between 10 inches and 18 inches, more preferably from 10inches to 14 inches and most preferably 12 inches to allow the feet ofthe subject 52 to be properly positioned while in the static posefixture 10. The width of the first and second foot alignment struts 16and 18 is preferably 1 inch to 3 inches, more preferably 1.5 inches to2.5 inches and most preferably 2 inches. The first and second footalignment struts are preferably at least 1 inch in thickness and areattached to the base 12 of the static pose fixture 10 using screws, nutand bolt, or any other well-known means thus enabling adjustment of thefirst and second foot alignment struts 16 and 18.

Each of a first vertical strut 20 and a second vertical strut 22 areattached to the upper exterior portion of the base 12 at one end of thestrut length. The first and second vertical struts 20 and 22 arepreferably parallel to each other and placed at least 4 inches from therear portion of the base. The first and second vertical struts 20 and 22are attached to the base using a nut and bolt, screw or any other wellknown fastening means. The vertical struts 20 and 22 are preferably atleast 66 inches in length and extend substantially perpendicularly upfrom the base 12 along the length of the strut. The first vertical strut20 is located on the outer exterior portion of the first foot alignmentstrut 16 and the second vertical strut 22 is located on the outerexterior portion of the second foot alignment strut 18. The distance d′between the first and second vertical struts 20 and 22 is at least 12inches to support the subject 52 in an upright and comfortable position.Additionally, the first and second vertical struts 20 and 22 arepreferably between 2 inches and 8 inches in width, more preferably 3inches to 6 inches and most preferably 4 inches in width to providestructural stability. The first and second vertical struts 20 and 22 arealso preferably 1 inch to 4 inches in thickness, more preferably 1 inchto 3 inches and most preferably 2 inches.

A lower back strut, 24 is preferably located at least 30 inches abovethe upper exterior surface of the base 12 in a horizontal plane betweenthe first and second vertical struts, 20 and 22 to further stabilize thesubject 52 while in the static pose fixture 10. The lower back strut 24should preferably extend at least 15 inches in length for attachment tothe first and second vertical struts 20 and 22 at each end and shouldpreferably be at least 2 inches in width and preferably at least 1 inchin thickness to provide support for the back of the subject 52. Thelower back strut 24 may optionally include a strap, belt or other devicefor locking the subject 52 in place during the measurement.

As illustrated in FIGS. 1 and. 7, a first grip 26 is attached to thefirst vertical strut 20 using a first slider strut 30 on an exteriorportion. A second grip 28 is attached to the second vertical strut 22using a second slider strut 32 along the exterior portion. The first andsecond grips 26 and 28 are substantially perpendicular to the first andsecond vertical struts 20 and 22 and substantially parallel to the base12. The slider struts 30 and 32 permit the first and second grips 26 and28 to move vertically along the length of the first and second verticalstruts 20 and 22. The first and second slider struts 30 and 32, areattached to the first and second vertical struts 20 and 22 with a linearbearing (not shown), however any method that allows the strut to slideup and down may be used including nut and bolt, screw attachment, slidelock and key, bands, pulleys, or levers. The first and second grips 26and 28 are preferably positioned at least 15 inches above the base 12.The distance between the first and second grips 26 and 28 is between 18inches and 36 inches, preferably between 20 inches and 32 inches andmost preferably between 21 inches and 30 inches. The first and secondgrips 26 and 28 may be covered to cushion the subject's 52 hands byneoprene, fabric, rubber, foam or other well-known materials to providecushioning support.

Alternatively, as illustrated in FIG. 6, the static pose fixture 10 hasfirst and second upper arm supports 34 and 36, in place of the first andsecond grips 26 and 28, thereby supporting the left and right arms ofthe subject 52 during the measuring process. The first and second upperarm supports 34 and 36 are attached to the rear portion of first andsecond arm alignment struts 40 and 42. The first and second upper armsupports 34 and 36 are attached to each of the first and second verticalstruts 20 and 22 a distance of at least 40 inches from the base 12. Thefirst upper arm support 34 has a right end extending laterally outwardfrom the first vertical strut 20 and the second upper arm support 36 hasa left end extending laterally outward from the second vertical strut22. At least one linear bearing 38 is located on the first and secondupper arm supports 34 and 36 to allow the first and second upper armsupports 34 and 36 to move up and down along the length of the first andsecond vertical strut 20 and 22 to support a subject 52 of any size inthe proper orientation. The linear bearing 38 should not allow the firstand second upper arm supports 34 and 36 to sag, as the measurements aredependent on the arms being in a parallel 90° angle with respect to thesubject's 52 body.

The first arm alignment strut 40 is preferably substantiallyperpendicular to the first upper arm support 34 at a right end and thesecond arm alignment strut 42 is preferably substantially perpendicularto the second upper arm support 36 at a left end. The first and secondarm alignment struts 40 and 42 are in relation to each other along anelongated strut 44 which is attached to the rear portion of the firstand second vertical struts 20 and 22 and also attached to the first andsecond arm alignment struts 40 and 42 at a right end for the first armalignment strut 40 and a left end for the second arm alignment strut 42.The elongated strut 44 is preferably located at least 40 inches upwardfrom the base 12 and is preferably at least 18 inches in length. A headand upper back support 46 is attached to the elongated strut 44 at amid-point. The head and upper back support 46 extends substantiallyperpendicularly away from the elongated strut 44 to an unattached end.The head and back support 46 is preferably at least 12 inches in lengthand 3 inches in width to comfortably support the subject's back and headin a steady state position during the measuring process.

The static pose fixture 10 preferably contains at least two sliders 48,located on any of the first and second vertical struts 20 and 22, firstand second foot alignment struts 16 and 18, or alternatively on any ofthe first and second upper arm supports 34 and 36, first and second armalignment struts 40 and 42, and head and upper back support 46.

As illustrated in FIG. 9, the slider 48, is preferably composed ofaluminum, aluminum alloy, composite, steel, or other material. Theslider 48 is preferably shaped in a rectangular or block formation,however it is not limited to this formation. The slider 48 contains atleast one reflective means 50 bonded to it. The reflective means 50 ispreferably bonded to the slider 48 using epoxy, solder, or otherwell-known means. The slider 48 moves freely along the length of thestrut along grooves 49 located in the strut length. The slider 48 isadjusted along the length of the strut using a nut and bold, hex and keyor any other well-known means. One slider 48 is preferably aligned witha major joint segment of a subject's 52 body, while another slider 48 isaligned with a different joint segment of the subject's body therebyincreasing the accuracy of determining the length between the subject's52 limbs by calculating the distance between two sliders 48.

The static pose fixture 10 is preferably constructed of aluminum,aluminum alloy, steel, or other material providing the requisitesturdiness to support the subject 52 during the modeling process.Extruded aluminum is most preferable as it provides the optimum weightand durability required.

As illustrated in FIG. 8, to optimize motion capture modeling using thestatic pose fixture 10, a subject 52 is placed in a marker interfacesuit. This step involves attaching at least one body plate 58 to thesubject 52 at various joint locations. The body plate is preferablyattached to the subject 52 using clamps, elastic bands, straps, clasps,hook and loop closures or any other well-known means. A preferred methodinvolves wrapping lengths of stretch fabric around each limb of thesubject 52. An exemplary stretch fabric for this purpose is Velstretch®.Subsequently, at least one body plate 58 is attached to the stretchfabric using epoxy, snaps, velcro, or any other suitable means ofattachment. The body plate 58 may also optionally be cushioned againstthe subject's 52 limbs by attaching or placing rubber, foam, cloth, orany other material that provides cushioning effect to or between thebody plate 58 and the subject's 52 limb.

The body plate 58 is preferably composed of rubber, plastic, compositeor ceramic, as shown in FIG. 8, the body plate 58 of the presentinvention is preferably composed of a composite material. The compositematerial reduces the mass of the body plate 58, while providing a stablebase for mounting on the subject. Additionally, the composite materialis preferably molded to provide a curved body plate 58 permitting betterpositioning of the body plate 58 on the subject's 52 limbs. It ispreferable to use curved body plates 58 for this purpose, however thebody plates 58 are not limited to a curved configuration. The body plate58 preferably ranges from 0.50 inch to 3.0 inches in width, 2.0 inchesto 9.0 inches in length and 0.10 inch to 1.0 inch in height. The bodyplate 58 also preferably contains at least three markers 60 a-c, but maycontain as many as 15-20 markers for measuring the location of the bodyplate 58 on the subject 52. These markers 60 a-c are preferablyretro-reflective, active IRED, or magnetic, but are not limited to thesetypes. As illustrated in FIG. 8, one marker 60 in a body plate 58 isselected to be the origin of a localized coordinate system. The 3Dposition of each marker 60 on the body plate 58 is measured, and theposition and orientation of the body plate 58 is then reported withrespect to a global origin. Additionally, at least one marker 60 islocated on the base 12 of the static pose fixture 10 to act as an originpoint for the localized coordinate system in the event that one of themarkers 60 on the body plate 58 is obscured. The body plate 58 is thenconnected to a strobe box (not shown), which controls the marker 60illumination. The use of a curved body plate 58 in conjunction with atleast three markers 60 a-c on the body plate 58 alleviates the event ofcomplete marker occlusion thus insuring that at least one body platemarker 60 will be visible.

Once the body plate 58 has been attached to the subject 52, the bodyplate 58 locations are then optimized on the subject 52. With a motioncapture system active, the subject 52 swings a golf club 62 and the dataquality is evaluated by examining a chart of missing data. If less thanthree body plate markers 60 a-c on a body plate 58 are in view, thesystem will generate no data for the body plate 58 at that instant. Itis important that fast moving body plates 58 such as those on the armsare not occluded for more than 3 consecutive frames during the downswingor accuracy will be lost when the missing data is interpolated. If thisoccurs, body plates 58 that are occluded excessively are preferablymoved slightly, the subject 52 then swings again, and the data qualityis evaluated. This process is repeated until body plate 58 locationshave been optimized.

As illustrated in FIGS. 4 and 5, once the body plate 58 locations havebeen optimized, the subject 52 is then placed in the static pose fixture10. The subject 52 is constrained to a static position and orientationfor measurement of the geometry and marker location.

Joint center measurements are preferably obtained while the subject 52is in the static pose fixture 10 by using a digitizing probe 56 asillustrated in FIG. 10. By having the subject's 52 arms point down andthe hands wrap around the first and second grips 26 and 28 near thesubject's 52 hips. A digitizing probe 56 is preferably used to measurethe distance between various joint segment lengths including thesubject's wrist joints, which are often difficult to measure. Anexemplary digitizing probe is manufactured by Northern Digital, whichmeasures the position of the probe tip with respect to a selectedobject. The probe 56 is preferably used to mark at least four locationson a subject's 52 body thereby recording the position and orientation ofvarious joint segments on the subject's 52 body with respect toposition, providing positional coordinates and angularity, which ispreferably used to set a coordinate system with respect to the globalorigin. A computer program calculates the length and orientation of eachbody segment from the digitizing probe measurements, to build thecomputer model 64 of the subject 52. Additionally, for more precisemeasurements while the subject 52 is in the static pose fixture 10, theposition and orientation of each of the rigid body plates 58 on thesubject 52 is preferably measured and recorded.

Alternatively, joint center measurements are obtained when the arms arepositioned shoulder height and the elbows are bent at 90° degree anglesaway from the body. The linear bearing 38 on the first and second armalignment struts 40 and 42 are raised or lowered so that the arms resthorizontally. The linear bearing 38 on the first and second armalignment struts 40 and 42 nearest the elbows of the subject 52 are thenmoved toward or away from the shoulders so that the elbows rest againstthe first and second arm alignment struts 40 and 42. A slider 48 with atleast one means 50 bonded to it is then placed on the first and secondarm alignment struts 40 and 42 corresponding to each major joint centeron the subject's 52 arms. A slider 48 is also placed on the first andsecond vertical struts 20 and 22, first and second foot alignment struts16 and 18, first and second arm supports 34 and 36 and head and upperback support 46. The slider 48 is adjusted to align with the appropriatejoint center and locked in place. A motion capture system is then usedto measure the 3D coordinates of the sliders 48, as well as the positionand orientation of each of the rigid body plates 58 mounted to thesubject 52. The distance between two sliders 48, such as those alignedwith the wrist and elbow is calculated and the result is the length ofthe corresponding limb, in this case, the forearm. The length of eachlimb is determined by the computer, which calculates the distancebetween sliders 48. These lengths are then used to properly size segmentlengths in the computer generated player model 64. The body plate 58position and orientation data is used later to locate the motion agentson the swing model 64 and the measurements are later run into a computerprogram that calculates the length and orientation of each body segment,to build the computer model 64 of the subject 52. A model 64 ispreferably built with limb lengths based on the slider 48 measurementsand limb orientations assumed to be either 0° or 90°. Furthermore, usingthe rigid body plate 58 measurements obtained while in the static posefixture 10, each of the limbs and limb angles will be in the correctposition and orientation for the motion capture program.

Once the measurements have been determined, swing motion is preferablycaptured using a motion capture system and any experiment involvingmeasuring the swing motion of a player. If at any time the body plates58 move on the subject's 52 body, the subject 52 can re-enter the staticpose fixture 10 and a new frame of data is preferably collected. The useof the static pose fixture 10 makes resetting the body plate 58locations less time consuming and more accurate then was previouslyavailable by allowing the subject 52 merely to re-enter the static posefixture 10, re-set in the known position and realign the body plates 58.Additionally, the slider 48, which has already been locked in place forthe subject 52, is preferably used to re-align the subject 52 accordingto the pre-set slider 48 positions.

As illustrated in the graph of FIG. 11, during the capture of swingdata, each swing is post-processed using computer programming softwarethat fits plate position and orientation with a polynomial curve inorder to fill in any gaps in data that is missing due to an occludedmarker 60. An exemplary computer programming software package for datais MATLAB® software.

Next, a player model 64 is built using the measurement data obtainedwhile the subject 52 was constrained in the static pose fixture 10.Various computer software packages are preferably used to build a playermodel 64; one exemplary program is the ADAMS FIGMOD® software package.To build a player model 64, the height, weight and age of the subject 52is entered. The software uses this information to build a player model64 with average mass properties based on an anthropomorphic database.

Next a file with the limb length and orientation data and body plate 58position and orientation data previously collected is imported. Thesoftware uses the limb length data to automatically size each of themodel's 64 limbs.

Next the computerized player model 64 is brought into the static posefixture 10 posture. In this step, each of the model's 64 joint angles isadjusted to the same angles that were measured on the subject 52 whilein the Static Pose Fixture 10. Each limb of the model 64 now occupiesthe same space in the model 64 coordinate system as it did in themeasurement coordinate system.

As illustrated in FIGS. 12 and 13, motion agents are applied to themodel 64 while in the static pose posture. Illustrative spheresrepresenting origins of each of the rigid body plates 58 are linked toeach limb of the model 64 as measured using the static pose fixture 10.Later, minimizing the distances and angles between the data points andthe motion agents will control the model's 64 motion. With the model 64correctly sized and oriented in previous steps, motion agents are simplyloaded into space in the position and orientation measured while theplayer was in the static pose fixture 10. Each agent is then rigidlylinked to its corresponding limb.

The joint angles and limbs as defined by the body plate 58 locations ofthe player model 64 are rotated to bring the player into a pose that issimilar to a typical ball address position as illustrated in FIG. 14.This will make it easier for the software to bring the player into themeasured address position later.

Previously collected swing data is then imported and the first frame ofdata with the player in the address position is loaded into the softwareprogram.

Once the swing data is set, the computer program performs a staticanalysis to minimize the distance between the motion agents and the datapoints in the first frame of data. This brings the player model 64 intothe measured address position.

Additionally, position data points obtained using the digital probe 56are preferably loaded into the program. These points will show up inspace in the same location as previously measured. Points on the axes ofthe model's 64 joint segments are moved to the measured joint segmentpoints and locked in those locations. In addition, difficult to measurewrist data is incorporated into the program through measurementsobtained using the digital probe.

A club 62 is preferably selected for the player model 64 and aparametric model of the golf club 62 can be loaded and gripped by theplayer model 64. The selection of a particular club 62 allows theaffects that various club properties have on a player's swing to beevaluated as well as the performance of various products for aparticular swing.

Once the club 62 has been selected and assigned to the player model 64,the swing model is actuated. The player model 64 is preferably shown asa computer-generated model 64 or in a more animated form as illustratedin FIG. 15. The swing model allows the program to step through the swingdata frame by frame and maintain the minimum distance between the datapoints and motion agents. Effectively, this step causes the model 64 toreproduce the actual swing with a high degree of accuracy.

Additionally, joint torque values are determined using inverse dynamics,as performed in the ADAMS FIGMOD® program to calculates the torqueproduced by each joint throughout the swing based on the swing motionand mass and size properties of the player's limbs. Once the jointtorque values are assigned, the model 64 applies the joint torque valuesto the player model 64 through time, rather than minimizing the distancebetween motion agents and data points. In this mode, club properties canbe varied, and the affects of these variables on swing motion can bestudied.

From the foregoing it is believed that those skilled in the pertinentart will recognize the meritorious advancement of this invention andwill readily understand that while the present invention has beendescribed in association with a preferred embodiment thereof, and otherembodiments illustrated in the accompanying drawings, numerous changes,modifications and substitutions of equivalents is preferably madetherein without departing from the spirit and scope of this inventionwhich is intended to be unlimited by the foregoing except as may appearin the following appended claims. Therefore, the embodiments of theinvention in which an exclusive property or privilege is claimed aredefined in the following appended claims.

1. A system for measuring a person who is a subject of a motion capturemodel, the system comprising: a static pose fixture; a plurality ofmarkers positioned on the person; means for recording the position andorientation of each of the plurality of markers positioned on theperson; means for measuring the subject to generate a plurality ofmeasurements; means for converting the measurements into a localizedcoordinate system; and means for generating a computer model of thesubject based on the measurements.
 2. The system according to claim 1wherein the static pose fixture comprises: a base having a substantiallyflat surface; a pair of foot alignment struts located on the upper rearsurface of the base wherein the distance between a first foot alignmentstrut and a second foot alignment strut is at least 10.0 inches; a pairof vertical struts located on the upper rear surface of the base whereina first vertical strut is located on an outer exterior portion of thefirst foot alignment strut and a second vertical strut is located on anouter exterior portion of the second foot alignment strut; and a pair ofgrips attached to the pair of vertical struts and located at least 15inches above the base.
 3. A method for measuring the size of a motioncapture subject, the method comprising: placing the motion capturesubject in a marker interface suit having a plurality of markers;optimizing the position of each of the plurality of markers on themotion capture subject during a golf club swing by the motion capturesubject; constraining the motion capture subject in a static positionand orientation for measurement of the geometry and location of each ofthe plurality of markers; and capturing a swing motion of the motioncapture subject using a motion capture system.
 4. A method of measuringa subject which is an object of a motion capture model, the methodcomprising: attaching at least one body plate to the subject; optimizinga location of the at least one body plate; positioning the subject in astatic pose; measuring at least two joint segment lengths of thesubject; converting the measurements of the two joint segment lengthsinto a localized coordinate system; and generating a computer model ofthe subject based on the measurements of the two joint segment lengths.5. The method according to claim 4 wherein the positioning the subjectin a static pose comprises positioning the subject within a static posefixture.
 6. The method according to claim 5 wherein the static posefixture comprises: a base having a substantially flat surface; a pair offoot alignment struts located on the upper rear surface of the basewherein the distance between a first foot alignment strut and a secondfoot alignment strut is at least 10.0 inches; a pair of vertical strutslocated on the upper rear surface of the base wherein a first verticalstrut is located on an outer exterior portion of the first footalignment strut and a second vertical strut is located on an outerexterior portion of the second foot alignment strut; and a pair of gripsattached to the pair of vertical struts and located at least 15 inchesabove the base.